encountered the same problem today, and here's what i came up with that (surprisingly) worked for me:
- talked to the myconids / spore servants at the outskirts of the colony, through which the sovereign said that he wishes to speak to me
- left my companions there, so they wouldn't trigger the "get out of here" dialogue themselves
- drank an invisibility potion, walked up to the sovereign (the one treating the corpses on the mushroom in the middle of the colony) and talked to him
- i had already killed the duergars before so i told him that (therefore i'm not sure if that's required or if simply agreeing to help them would do the trick)
after that i was considered 'worthy' and so i could walk around the colony freely, without the potion
unfortunately i can't help with the baelen part as i didn't encounter the bug, but good luck with that!